There are many instances in the use of telescopes in which it is necessary or desirable to rotate the telescope about its polar axis at a constant rate. For example, because of the rotation of the earth, it is necessary to rotate an astronomical telescope about its polar axis at a constant rate of one revolution per day when making long time studies and photographs of celestial bodies.
A variety of mounting systems for astronomical telescopes have been devised. One of the most common astronomical telescope mounting system is known as the equatorial mount. The equatorial mount embodies a two-axes gimbel system having an inclined rotation axis which parallels the earth's rotational axis, and having a second horizontal rotational axis which intersects the inclined axis at right angles to a vertical plane containing the latter axis. The inclined axis is referred to as the polar axis of the telescope, and the horizontal axis is referred to as the declination axis. Rotation of the mounting unit about the declination axis adjusts the elevation angle of the telescope to correspond to the latitude at which the telescope is used. Rotation of the mounting unit about the polar axis moves the telescope in a rotary tracking motion.
An important objective of the present invention is to provide an improved, simple and inexpensive astronomical telescope drive assembly by which an astronomical telescope is rotated with extreme accuracy about the polar axis at a desired rate by a single low speed synchronous motor which is coupled directly through a worm gear on its shaft to a driven gear within the base of the telescope, the driven gear being coaxial with the polar axis.
The technique described in the preceding paragraph permits high precision accuracy to be achieved between the drive motor and the driven gear since it eliminates two potential sources of tracking error of the two reduction gears used in the prior art units. The technique also results in the elimination of the expense of the two reduction gears.